Stockholders' Equity - Changes in Ownership Interests (Detail)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Lazard Ltd [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Ending balance (in shares)	129,766,090	129,056,081	128,216,423
Percentage of Ownership, Ending Balance	100.00%	99.50%	98.80%
LAZ-MD Holdings [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Ending balance (in shares)		710,009	1,549,667
Percentage of Ownership, Ending Balance		0.50%	1.20%
Total Lazard Group Common Membership Interests [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Ending balance (in shares)	129,766,090	129,766,090	129,766,090